The present invention relates to a lubrication system, and more particularly to a rotary-wing aircraft power transmission system having a lubrication system which provides prolonged loss of lubricant (LOL) operation.
Rotary-wing aircraft power transmission systems incorporate a multitude of gears and bearings which are subject to heat, sliding and surface wear. Such conditions are significantly increased during loss of lubricant (LOL) operating conditions caused by, for example, ballistic damage, pump failure and system leaks. The primary components of a power transmission system which may be failure points under LOL conditions include bearings and gears which are constantly oil lubricated under normal conditions using pressurized oil jets or splash oil lubrication methods.
The United States Department of Defense (U.S. DoD) currently imposes a requirement that all rotary-wing aircraft power transmission systems operate for a predetermined period of time in a LOL condition. The requirement includes the capability to maintain flight operations for a relatively short time period such as 30 minutes during the LOL condition, albeit at reduced power levels, typically sufficient only to sustain level flight operations.
Various conventional emergency or auxiliary lubrication systems are known and practiced. Duplicate lubricating wicks and jets have been provided for lubricating individual components along with an auxiliary pump system. Air aspirated nozzles have also been utilized for delivering a stream of oil to each individual component. Even through relatively effective, these existing systems may result in additional weight, complexity, and design envelope, yet still not completely satisfy certain LOL requirements.
Accordingly, it is desirable to provide a lubrication system which facilitates operation of a power transmission system for a prolonged time period under LOL conditions.